The present invention relates generally to the field of adaptive control systems, and more particularly, to an electronic control unit for adaptively controlling the operation of a motor vehicle, where the electronic control unit retains values of control parameter correction factors learned during vehicle operation and can be transferred from one vehicle to another.
It is known that a microprocessor based adaptive control system can be utilized to greatly improve vehicle powertrain (engine and/or transmission) performance. In such systems, control parameters, such as those used for regulating idle air flow, engine fueling, spark timing, exhaust emissions, transmission shifting, etc., are generally initialized to predetermined mean values provided from a programmable read only memory (PROM) in an electronic control unit (ECU) when the vehicle is operated for the first time. Thereafter, correction factors for the control parameters are learned based upon known adaptive control algorithms when the vehicle is operational. The learned correction factors are then used to adjust the control parameters to optimized values, thereby improving vehicle response and drivability, while compensating for aging and variations in powertrain components due to production tolerances.
The learned values of correction factors are generally stored in a keep alive memory (KAM) in the ECU so they can be retained when the vehicle is not operational. In the past, the KAM has been provided by maintaining vehicle battery power to conventional random access memory (RAM) when the vehicle ignition system is switched off. One major disadvantage associated with using of this type of KAM for storage is that the learned values of the correction factors will be lost if the vehicle battery fails or is disconnected from the ECU.
Recently, electrically erasable programmable read only memory (EEPROM) devices have been used to replace the KAM for storing values of learned correction factors in vehicle adaptive control systems. The learned values for the correction factors are easily stored in the non-volatile EEPROM devices when the vehicle is not operational, and there is no risk of losing the stored values if the vehicle battery fails or is disconnected from the ECU.
The use of EEPROM for storing the learned correction factors has been found to present a problem in the vehicle servicing environment. A common service procedure used in diagnosing a potentially defective ECU involves transferring the ECU from a first vehicle that requires servicing to a second vehicle that is known to be operating properly. If the second vehicle is then found to operate improperly with the transferred ECU, it is concluded that the ECU is defective. However, this may not be correct due to the presence of the EEPROM device in the transferred ECU.
Since the EEPROM retains the values of the correction factors learned while operating the first vehicle, the adaptive control system of the second vehicle applies these same values to control its own powertrain. Due to the differences between the powertrain components in the first and second vehicles, it is quite possible for the second vehicle to operate improperly when its adaptive control system uses the retained correction factors learned for the first vehicle. This of course would lead to the erroneous conclusion that the ECU is malfunctioning, when it is actually operating properly.
In view of the foregoing, there exists a need for a method and apparatus for detecting when an electronic control unit is transferred from a first vehicle to a second vehicle and for preventing an adaptive control system in the second vehicle from using correction factors learned and stored in the electronic control unit while it was adaptively controlling the operation of the first vehicle.